2011 Nuevo toilet flush

I think I have an issue with the flush pump or the 12v supply to the flush pump. I've had intermittent issues with the 10A fuse that supplys both the toilet flush pump and the water fill connector (Whale). This fuse is located with the 12V fuses in the rectifier/consumer unit that is located in the wardrobe. Earlier in the year I found the fuse had gone but never got to the bottom of the problem. I've read about issues with flush pumps sticking, sometimes after periods of no use or possibly caused by using the pink additive in the flush tank.
We were away in The Lakes a few weeks back and had no problems until the day we left when once again the flush would not work and it was, again, the 10A fuse gone. On trying to replace it, it blows immediately. I did not add any flushing solution to the tank for this trip.
I'd like to ask if anyone can point me in the right direction here. I'm unsure whether it is in fact the pump. The reason being, the pump appears to be protected by a 3A fuse in the Thetford cabinet and that does not blow. I have noticed what appears to be a diode (Zener?) across the positive and negative supply leads within the Thetford cabinet that I assume feeds the flush pump (via its 3A fuse). I'm thinking that if this diode has broken down it is applying a short on the supply here which would cause the 10A fuse in the consuner unit to blow.
I'd like to know what the purpose of this diode is as it appears to be connected in a 'Heath Robinson' way, crimped into connectors on the wiring.
Can anyone help?

Cheers

The diode is a standard rectifier and suppresses a spark that would be caused as you release the flush switch. Sparking would wear the switch out.

If you have a multi-meter you can check the diode. Remove the 10A supply fuse and the 3A toilet fuse (assuming the diode is connected across the feed wires on the supply side of the 3A fuse). Connect the meter on the resistance range across the diode and note the reading, reverse the meter connections and repeat. In one direction the diode should read a low resistance (ohms) and in the other high (Megohms). If low in both directions the diode could be faulty and you will have to disconnect it and retest to be sure. If the diode test ok, then you have a wiring fault if the supply feed.

Thanks Peter , that's useful info